Ball-mill.



H. OSTWALD.

BALL MILL.

Arrmoulon FILED MAY 15, 1911.

Patented Nov. 5, 1912.

2 SHEETS-SHEET 1 H. OSTWZLD.

BALL MILL.

APPLICATION FILED MAY 15, 1911. 1,043,349, Patented N0v.5, 1912.

2 SHEETS-SHEET 2 UNITED STATES PATENT OFFICE.

CE os'rwasirpllonmcnx, (1mm.

To all whom it may concern:

Be it known that I, Hnnnucn' Osrwm, subject of the Em eror of Germany, residat Cologne, erman have invented certain new and useful l Ball-Mills, of which the following is a specification. I a I The present invention relates to ball-mills, belonging to one of the most important classes 0 disintegrators, but which, nevertheless, in the known constructionalforms yield a ve'rly low efliciency. According to the princip e upon which hitherto the construction of such ball-mills has been based, the interior surface of the mill-drum is provided with projecting ribs, steps, or such like device, WhlCh, intheir rotation, with the drum, raise the balls until they drop out of the recesses so formed and on to the material which ,is to be crushed. These ribs or other project-ions leave dead spaces which are lost to the process of disintegration. By increasing the height of such ribs, not only are the dead spaces edfpally increased but the ribs will also li t an increased amount of material out of reach of the disintegrating action. Furthermore the mill cannot be worked at anything like high speed, as, if such were the case, the balls would receive a flinging impetus and thus be violently thrown against the bare grinding projections, while concurrently the grist would be lifted too high. This should be avoided because when the material is thus raised by the ribs orrojections, the center of gravity is considera ly displaced with the result that a very high expenditure of power incomparison to the attained grindmg efllciency 18 required.

According to the present invention the mill-drum may have an absolutely lain innor surface, as the balls are-raised y mag netic force excited from theinterior and when they have reached any desired height,

the attractive power is automatically cut out, so that the balls are released and may fall down unhindered on the material they are intended to crush.

In the accompanying drawings Fi re 1 shows an example of a constructiona form of ball mill according to this invention. Fig. 2 shows a modification. Fl. is an example of a ball mill of the kin hitherto in use. Fig. 4 shows in transverse section 5 an example of a preferred form of-ball mill' according to the present invention. Fig. 5

Specification o! Patent.

Application me m 15, 1911. mm m. mam.

I mprovements 1n shows the some in longitudinal section. F196 shows diagrammatically an arran' nent of automatic switches for magnetiz- 1n and de-magnetizing the electromagnetsferring to Fig. l in this example the cylmdrlcal mill-dram is formed by metal plates a, set together longitudinally which during the rotary motion of the drum pass in front of stationary electro-magnets b, the latter being so placed as to affect the said plates mainly during the rising half of their rotation and by the influence of which thfiy become secondary poles and attract the ba s or weights until they reach point 0, when getting beyond the influence of themagnets they lose their power of attraction and al low the balls to drop. Fig. 2 is an example of modified constructional form. In this case a number of electro-magnetsare arranged in a circle, so as to embrace the whole circumference of the mill-drum and to rot-ate with the same. Midway between each pair of magnets the coil is reversed as at d. Each second metal plate e thus forms a pole-shoe for one ole of the magnetic system, the interme' iate metal plates f. then becoming effective opposite poles. Each coil 9. is separately energized. For this purpose the conductors are connected to brushes h. which are adapted to slide on a stationary contact rin i. and a: similarly stationary segment k. he lengthof the latter is determined by period the magnetic field is desired to last, that is to say the current continues to flow through the several coils for such period as the curcuit may be closed by contact of the brushes h. with the ring i. and'the segment k. respectively. A number of segments is. of varying lengths for each of the coils, might be arranged in such a way that the respective brushes h. maintain contact with the several coils for varying eriods, (corresponding to the varying lengths of the segments) and consequently the balls are 0 on their outer ends, which bolts pass through bars 1) connecting the magnets of Patented Nov. 5, 1912.

each row, such bar being supported by a casing g the lower edge of who rests upon the face of the drum. The magnets are preferably insulated from the drum by sleeves r of suitable material. The parts of the drum between the rows of magnets are perforated for the sifting awa ofthe finely ground particles which, a ter' a further sifting through an outer drum 8, fall into the d15- charge hopper t. The rough material is fed into the mill through the hopper u and passes into the drum through a worm-lined tube a which is an extension of the cover plate won one end of the drum and revolves therewith in a bearing an. The drivin shaft is fixed into the oppositecover p ate a. In this example the contact stri s (shown in Fig. 6) are arranged in the orm of concentric segments l, 2, 3, 4, 5, and a ring 6, upon a disk of insulating material adapted to revolve with the drum upon the same axis. Each of the segments is electrically connected with the negative pole of the battery, the magnetic coils forming part of the circuits. A stationary conducting bridge piece 7 bears contact brushes 8, 9, 10, 11, 12, 13, while the ring 6 is connected with the positive pole of the battery. As the drum revolves one or other of the segments passes under its brush and the corresponding circuit is closed by the connecting bridge thus energizing the row of magnets in that particular circuit. When that segment has completed its passage under the brush the circuit is automatically re-opened and the magnets tie-magnetized. The segments are so arranged that each of. them begins to ass under the brush when the correspon ing row of magnets is in position 15 and completes its passage when the. row has nearly arrived at position 18. The halls will thus be carried through about half a revolution and dropped from nearly the highest level. In arranging the coils 1t is desirable that they should alternate in direction of winding so as to form alternate magnetic poles and thus provide the greatest efiiciency.

A comparison between Fig. 3 and Figs. 1, 9 and 4, shows clearly what considerable economic advanta es may be gained-by the new invention; a vantages, which may be summed up as follows: 1. The possibility of using a drum having a perfectly plain inner surface enables the center of gravityof the material, which is being disinte ated, to remain more central with the res t of a lower expenditure of power. 2. As the. balls do not roll back but strike onthe ist from any desired height not a laceratmg, but as it should be in a ball mill-a breaking action is attainedand simultaneously an economy of motive power. 3. Inasmuch as the balls do not roll back, they produce no friction with the interior surface of the drum so that the latter is exposed in a much smaller degree to wear and tear, and may therefore be constructed of lighter material, resulting in electric current required for developin t this respect in a saving of motive power, the V magnetism is so small compared wit e re sult-ing economy in motive power, that it is hardly worth taking into account. The finished product may be dischar d in any known manner, by means of per orations in the metal plates, or through spaces between the metal lates, or on the end face opposite to the feed? Having thus described my invention'what I claim is 1. A ball mill comprising in combination a rotatable drum forcontaining-the mate-. rial to be crushed, iron balls or weights inside said drum, stationary electroma 'ets facing the inner circumference of said rum or a portion thereof, and adapted to hold the said balls or weights to the inner surface of said drum only until they have been.

carried nearly to .the highest position in the drum, substantially as shown and described.

2. A ball mill comprising in combination, a rotatable drum for containing the material to be crushed, iron balls or weights inside said drum, electromagnets fixed on the outer circumference, means for magnetizing and de-magnetizing said magnets at convenient stages of their rotation with the drum so as to hold the said balls or weights to the inner surface of said drum and to release them when at a suitable height so as to drop upon the material to be crushed, substantially as shown and described.

3. A ball mill comprising in combination, a rotatable drum containing the material to be crushed, iron balls or weights inside said drum, electromagnets set in longitudinal rows and having heads protruding within the said drum, and means for magnetizing and de-magnetizing said ma ets at suitable stages of their rotation wit the drum.

4. A ball mill comprising in combination, a rotatable drum for containing the material to be crushed, iron balls or weights inside said drum, electromagnets set in longitudinal rows and havin heads protruding within the said drum an means for magnetizing and tie-magnetizing said magnets at suitable stages of their rotation with the drum, said means consisting of a rotatable disk provided with insulated concentrically disposed contact stri s of segmental shape brushes engaging said strip to energize said electromagnets only during such stages of the revolution of the magnets as are suit able for the purpose of carrying the said balls to the desired height, substantially as shown and described.

5. A ball mill of the class described comprising in combination, a rotatable drum mechanism adapted to contain the material to be crushed, and crushing elements loosely disposed in said drum mechanism, said drum mechanism being provided with electrical means for attracting and carrying said elements with said mechanism through one period of its rotation and then permitting said elements to fall upon the material, substantially as described,

6. A mill of the class described comprising in combination, a rotatable drum mechanism adapted to contain the material to be crushed and having a smooth interior surface, and crushing elements loosely disposed in said drum mechanism, said drum mechanism being provided with electrical means for attracting and holding said elements against-its interior during a portion of its rotation and then permitting said elements to fall by gravity upon the material, substantially as described.

7. A mill of the class described comprising in combination, a rotatable drum mechanism adapted to contain the material to be crushed, and crushing elements loosely disposed in said drum mechanism, said drum mechanism being provided with electrical 'means projecting into the interior thereof for attracting and carrying said elements with said mechanism through one period of its rotation and then permitting said elements to fall 11- on the material, substantially as describe 8. A mill of the class described comprising in combination, a rotatable mill drum adapted to contain the material to be crushed, crushin elements looselydisposed in said drum, e ectrical devices carried by said drum, and electrical mechanism for energizing said devices during one period of the drums rotation to attract and carry F said elements above the material and then successively dener izing the uppermost devices to permit sai elements to fell by gravity onto the material, substantially as described.

.In testimony whereof, I aflix my signature in the presence of two witnesses.

HEINRICH OSTWALD.

W'itnesses:

PAUL DAJ'LER, LOUIS KANDORY. 

